The invention relates to a method for editing a high-rate convolutional code for transmission and its reconversion at the receiver using code puncturing and serially adding the n-output bit streams (n=2, 3, . . . ) of a convolutional encoder. Such a method is known from "Conference Proceedings of the 6th International Conference on Digital Satellite Communications", Phoenix, Ariz., USA, September 1983, p. XII/24-31, for use in digital satellite communications.
High-rate convolutional codes can be generated basically in two ways:
a. by use of a high-rate encoder, and
b. by application of punctured coding to a low-rate code.
In punctured coding, single bits are deleted at intervals in a low-rate convolutional code. FIG. 1 shows the principle of such punctured coding. The source bits I are written into the register Reg of the encoder; see FIG. 2. The output bit streams Q.sub.1 and Q.sub.2 of the encoders are received by adders which link the parallel outputs of the register cells. A puncturing coder or puncturer Pu, which can be described by a puncturing algorithm, suppresses those bits for which the algorithm contains a 0 and transmits those bits for which the algorithm contains a 1. If every fourth bit is deleted from a code with the rate 1/2, a code of the rate 1/2.multidot.4/3=2/3 is created (FIG. 1).
Punctured codes can be decoded the same as the originally non-punctured code of the rate 1/n, and may permit a selection of two (instead of 2.sup.n-1) possible paths for each state. At the receiver, a de-puncturer for a punctured code is provided ahead of the decoder, by means of which so-called "dummy bits" are inserted in place of the previously deleted bits, which do not influence the metric calculation (See page XII/25, first column in the previously cited publication).
It is known from "IEEE Transactions on Communications", Vol. COM-32, No. 3, March 1984, pp. 315-319, to derive higher rate convolutional codes by puncturing from a code of a rate of 1/2. The higher rate may be varied or selectively used by selectively varying the puncture rate and/or selectively puncturing the code, according to propagation conditions.